1. Field of the Invention
The present invention relates to a DSRC (dedicated short-range communication) car-mounted equipment such as the one for collecting the toll used for an ETC (electronic toll collection) system in an ITS (intelligent transport system). More specifically, the invention relates to a DSRC car-mounted equipment which diagnoses disorder related to the collection of toll through the transmission/reception circuit to inform abnormal condition.
2. Prior Art
There has heretofore been known a DSRC car-mounted equipment (hereinafter often referred to simply as xe2x80x9ccar-mounted equipmentxe2x80x9d) that executes communication with an on-the-road equipment installed on a road on which a vehicle travels to transmit and receive various data.
In the DSRC car-mounted equipment and, particularly, in the ETC car-mounted equipment of this kind, the ETC function is invalidated when a transmission/reception circuit in the car-mounted equipment is not working well, which may become a cause of vehicle jamming at the toll gate. It is, therefore, desired that the function of the transmission/reception circuit is automatically checked in advance and that the driver is informed of the checked result.
In a device taught in, for example, Japanese Unexamined Patent Publication (Kokai) No. 307332/1996, the communication probability is operated by the on-the-road equipment based upon the communication between the on-the-road equipment and the car-mounted equipment to judge the disorder of the on-the-road equipment.
However, the device disclosed in the above publication has not been equipped with a function for judging the disorder of the transmission/reception circuit of the car-mounted equipment.
As described above, the conventional DSRC car-mounted equipment is not capable of checking the function of the transmission/reception circuit in the car-mounted equipment, and is not, hence, capable of informing the driver of the checked result.
The present invention was accomplished in order to solve the above-mentioned problem, and its object is to provide a DSRC car-mounted equipment which is capable of informing the driver of the condition of the data transmission/reception function to and from the on-the-road equipment, so that the driver will not enter into the toll road without knowing the disorder of the circuitry of the car-mounted equipment.
A DSRC car-mounted equipment according to the present invention comprises:
a transmission/reception antenna for executing communication with an on-the-road equipment installed on a road;
a transmission/reception change-over switch for changing over the transmission/reception function of the transmission/reception antenna;
a transmission/reception circuit including a reception circuit and a transmission circuit selectively connected to the transmission/reception antenna via the transmission/reception change-over switch;
a first local oscillator for generating a car-mounted equipment frequency related to the transmission/reception circuit;
a demodulator for detecting the electric field intensity and for picking up reception data from a signal received by the reception circuit;
a car-mounted controller for fetching the reception data by controlling the change-over of the transmission/reception change-over switch, and for sending transmission data to the transmission circuit;
an information output means connected to the car-mounted controller; and
a second local oscillator that outputs, to the transmission circuit, a frequency for detecting abnormal condition corresponding to an on-the-road equipment frequency transmitted from the on-the-road equipment; wherein
the car-mounted controller includes an abnormal circuit judging means for judging the condition of the transmission/reception circuit by using the frequency for detecting abnormal condition; and
the abnormal circuit judging means judges the transmission/reception circuit to be abnormal and drives the information output means when at least either the electric field intensity or the reception data detected based upon a leakage power of the frequency for detecting abnormal condition is not satisfying a predetermined condition in a state where the transmission/reception change-over switch is connected to the reception circuit.
The DSRC car-mounted equipment according to the present invention further comprises an abnormal condition detector switch which selectively connects the first or the second local oscillator to the transmission circuit; wherein
the second local oscillator outputs a frequency equal to the on-the-road equipment frequency as a frequency for detecting abnormal condition; and
the abnormal circuit judging means judges the condition of the transmission/reception circuit by comparing the electric field intensity detected based on a leakage power of the frequency for detecting abnormal condition with a predetermined value in a state where the abnormal condition detector switch is connected to the second local oscillator side.
In the DSRC car-mounted equipment according to the present invention, the abnormal condition detector switch is connected to the second oscillator when the power source circuit is closed, the second local oscillator is driven when the power source circuit is closed, and the transmission circuit is turned off when the power source circuit is closed.
In the DSRC car-mounted equipment according to the present invention, the abnormal circuit judging means sends a predetermined data that has been set in advance to the transmission circuit, and judges the condition of the transmission/reception circuit by comparing the electric field intensity and the reception data with a predetermined value and the predetermined data, the electric field intensity and the reception data being detected based on a leakage power of a frequency for detecting abnormal condition ASK-modified with the predetermined data.
The DSRC car-mounted equipment according to the present invention further comprises:
a mixer for detecting abnormal condition inserted between the first and second local oscillators and the transmission circuit; and
a filter inserted between the mixer and the transmission circuit to permit the passage of the on-the-road equipment frequency and the car-mounted equipment frequency only; wherein
the second local oscillator is selectively driven and outputs, as the frequency for detecting abnormal condition, an intermediate frequency which is a difference between the on-the-road equipment frequency and the car-mounted equipment frequency; and
the abnormal circuit judging means judges the condition of the transmission/reception circuit by comparing the electric field intensity detected based on a leakage power of the frequency for detecting abnormal condition with a predetermined value when the second local oscillator is driven.
In the DSRC car-mounted equipment according to the present invention, the second local oscillator is driven when the power source circuit is closed, and the transmission circuit is turned off when the power source circuit is closed.
In the DSRC car-mounted equipment according to the present invention, the abnormal circuit judging means sends a predetermined data to the transmission circuit, and judges the condition of the transmission/reception circuit by comparing the electric field intensity and the reception data with a predetermined value and the predetermined data, the electric field intensity and the reception data being detected based on a leakage power of a frequency for detecting abnormal condition ASK-modified with the predetermined data.
In the DSRC car-mounted equipment according to the present invention, the first and second local oscillators include a common reference frequency oscillator for outputting a reference frequency inclusive of the intermediate frequency, the first local oscillator has a frequency multiplier for forming the car-mounted equipment frequency from the reference frequency, and the second local oscillator has a second filter for picking up the intermediate frequency from the reference frequency.
In the DSRC car-mounted equipment according to the present invention, the information output means includes at least either a buzzer or a display unit to inform the abnormal condition of the transmission/reception circuit by voice or display.
The DSRC car-mounted equipment according to the present invention further comprises an external storage medium connected to the car-mounted controller to transmit and receive data related to the toll collection, wherein the car-mounted controller exchanges the data related to the toll collection between the on-the-road equipment installed on a toll road and the external storage medium, and automatically executes the toll collection processing based on the data related to the toll collection.